Adaptive display refresh and data compression in a radio frequency environment

Abstract

An adaptive display refresh and data compression solution for use in an RF network environment is described, where a network controller and portable terminals maintain an adaptive history of commonly used past information in order that it may be repeated quickly and communication speeds can be increased. A network controller maintains a separate history for each of the terminals in the RF network, and transmits a coded reference for the activities that are contained in the history, which is stored in the memory of both the controller and the portable terminal. Terminals and the controller additionally may negotiate to determine the data compression features which will be supported in communication between the two devices. Data is compressed according to the present invention by utilizing a hybrid run length and sliding dictionary compression scheme. Data is pre-compressed by a run length compressor, and is further compressed by a specialized sliding dictionary technique designed to minimize memory storage and transmission time requirements, resulting in an efficient data compression method requiring little additional storage.

What is claimed is: 
     
       1. A method of compressing data comprising: (a) first implementing a run length compression scheme to output repeated characters in a stream of input data as flags followed by a count of the number of repetitions;   (b) second implementing a sliding dictionary scheme to output a character itself if it is occurring for the first time in the stream of input data, and to output a pointer to a character sequence if the character sequence has already occurred in the stream of input data;   (c) formatting the output of step (b) by adding an additional bit to each character or pointer to indicate whether it represents a character or a pointer;   (d) accumulating the additional bits into a first byte of a set of data bytes to indicate whether each byte in the set is a character or a pointer, and   (e) transmitting the first byte of additional bits, and then transmitting further bytes of the set which are indicated as a character or a pointer by the additional bits of the first byte, such that data communication speed is improved to enable real time communication with minimal memory storage used.   
     
     
       2. The method of claim 1, wherein data compression occurs in the same location as data packet fragmentation. 
     
     
       3. The method of claim 2, wherein data is compressed in a network controller of a wireless communication system. 
     
     
       4. The method of claim 1, wherein data expansion occurs in the same location as data packet assembly. 
     
     
       5. The method of claim 4, wherein data is expanded in a portable terminal of a wireless communication system. 
     
     
       6. A method of compressing data comprising: (a) effecting a compression step to output repeated characters in a stream of input data as flags followed by a count of the number of repetitions;   (b) supplying as output a character itself if it is occurring for the first time in the stream of input data and supplying as output a pointer to a character sequence if the character sequence has already occurred in the steam of input data;   (c) formatting the output of step (b) to indicate for a set of data bytes, whether each byte in the set is a character or a pointer, and   (d) transmitting pointer information as a variable number of bytes adapted to the length of respective sequences.   
     
     
       7. The method of claim 6, wherein data compression occurs in the same location as data packet fragmentation. 
     
     
       8. The method of claim 7, wherein data is compressed in a network controller of a wireless communication system. 
     
     
       9. The method of claim 6, wherein data is compressed in a network controller of a wireless communication system. 
     
     
       10. The method of claim 6, wherein data expansion occurs in the same location as data packet assembly. 
     
     
       11. The method of claim 10, wherein data is expanded in a portable terminal of a wireless communication system. 
     
     
       12. The method of claim 6, wherein data is expanded in a portable terminal of a wireless communication system. 
     
     
       13. A data compression system comprising: (a) a data output processor capable of generating at least three different types of data output, wherein: the first data output compresses repeated characters in a stream of input data into a flag followed by a count of the number of repetitions in the stream,   a second data output supplies the output of a character as itself if the character has occurred for the first time in the stream of input data, and   a third data output supplies the output of a pointer of a variable number of bytes if a character sequence has already occurred in the stream of input data, and     (b) a format indicator for determining and identifying one type of output from another.   
     
     
       14. The data compression system of claim 13, wherein data compression occurs in the same location as data packet fragmentation. 
     
     
       15. The data compression system of claim 14 wherein data compression occurs in a network controller of a wireless communication system. 
     
     
       16. The data compression system of claim 13 wherein data compression occurs in a network controller of a wireless communication system. 
     
     
       17. A data expansion system comprising: (a) a data processor capable of expanding at least three different types of compressed data, wherein: the first type of data represents a string of repeated characters and is comprised of a flag followed by a count of the number of repetitions in the string of repeated characters,   the second type of data is comprised of a character represented as itself, and   the third type of data is comprised of a pointer with different numbers of bytes which refers to the position and length of strings of characters in a stream of data, and     (b) a format indicator for determining and identifying the second and third types of data.   
     
     
       18. The data expansion system of claim 17, wherein data expansion occurs in the same location as data packet assembly. 
     
     
       19. The data expansion system of claim 18, wherein data expansion occurs in a network controller of a wireless communication system. 
     
     
       20. The data expansion system of claim 17 wherein data expansion occurs in a network controller of a wireless communication system.